Molecular imaging with SERS-active nanoparticles.

Abstract

Raman spectroscopy has been explored for various biomedical applications (e.g., cancer diagnosis) because it can provide detailed information on the chemical composition of cells and tissues. For imaging applications, several variations of Raman spectroscopy have been developed to enhance its sensitivity. To date, a wide variety of molecular targets and biological events have been investigated using surface-enhanced Raman scattering (SERS)-active nanoparticles. The superb multiplexing capability of SERS-based Raman imaging, already successfully demonstrated in live animals, can be extremely powerful in future research where different agents can be attached to different Raman tags to enable the simultaneous interrogation of multiple biological events. Over the last several years, molecular imaging with SERS-active nanoparticles has advanced significantly and many pivotal proof-of-principle experiments have been successfully carried out. It is expected that SERS-based imaging will continue to be a dynamic research field over the next decade.

In vivo SERS detection of EGFR. a) A photograph showing the experimental setup where in vivo SERS spectra were obtained from the tumor and the liver. b) SERS spectra obtained from the tumor and the liver by using EGFR-targeted (left) or non-targeted (right) SERS-active nanoparticles. Adapted from Ref. [33].

SERS imaging of cell nucleus. a) Merged SERS and optical transmission image of a cell after incubation with a nuclear-targeting SERS-active nanoprobe. The arrows indicate the positions where the spectra in b) were collected. Scale bar: 10 μm. The inset is a cell incubated with non-targeted nanoparticles. b) SERS spectra obtained from the nucleus of a single living cell incubated with the nuclear-targeting SERS-active nanoprobe at different locations. Adapted from Ref. [75].

SERS imaging of pH in live cells. a) A photograph of a cell after incubation with the gold nanosensor. Lysosomal accumulations of gold nanoparticles are observed as black spots. b) pH map of the cell displayed as false color plot of the ratios of the SERS lines at 1423 and 1076 cm−1. The values in the color scale bar determine the upper end value of each respective color. Dark blue color indicates that no detectable SERS signals exist. c) Representative SERS spectra collected in the endosomal compartments with different pH. Adapted from Ref. [84].